Essential fatty acids
Despite its maligned media image, fat is one of several vital nutrients in our diet. We need fats for many important functions in the body. Cholesterol, for example, is the building block for all of our reproductive hormones. Cholesterol and fatty acids compose the cell wall of every cell in our body.
Our body can manufacture several types of fat and cholesterol from other substances, but certain fats cannot be produced inside the body: linoleic acid and alpha-linolenic acid. These fats are referred to as “essential fatty acids” because our body cannot manufacture them, yet they are essential for normal, healthy bodies. We must provide these essential nutrients in our diet.
What’s the difference between a fat and an oil?
I have a family member who insists the margarine he liberally spreads on his toast “ . . . is not fat.” Despite numerous explanations, he is convinced that vegetable oils and fats are two completely different food groups. So what is the difference between a fat and an oil?
Not much. The main difference is the number of double bonds or “links” in their chains, and how solid or fluid the substances are at room temperature. Fats are made of glycerin, which has three “arms” with a chain of fatty acids attached to each arm.
What do “chains” have to do with fats and oils? Fats and oils are made of long chains of carbons with hydrogen atoms attached. Think of them as long trains, with each carbon representing a boxcar on the train. At the “engine” end of the train are three chains ending in “CH2” groups. At the caboose end are three –COOH groups, which makes that end acidic. This acidic tail explains why these long chains/trains are named “fatty acids.”
Imagine the “hitches” between the boxcars as single or double connections, or “bonds” to use chemistry terms. The fewer the double hitches between the boxcars, the more solid the fat is at room temperature. Fats have only single “hitches” between the carbon atoms, which explains why they are solid at room temperature.
At the double hitches or “bonds,” the carbon atoms are loosely attached to each other. Johanna Budwig M.D., who has spent her life conducting pioneering research on fats and oils, describes these double hitches on the chain as “ . . .fragile there, loose; it absorbs water easily – as if you were to fray a smooth silk thread in one place and then draw it through water. The frayed part absorbs water, or dye, more easily. In the same way, these fatty acid chains with their weak, unsaturated connections, form protein associations very easily. The fatty acids become water soluble through this association with protein.”1
When we eat fats and oils, they travel across the intestines into the bloodstream. Remember that blood is a watery substance, and oil and water usually do not mix. These unsaturated fats, however, can become water soluble through their association with protein. Because these unsaturated fats with their double hitches between the boxcar can become water soluble, they are healthier forms of fat.
In contrast saturated fats cannot dissolve in the watery fluid of the blood. Hydrogenated oils, discussed in more detail below, also are insoluble in water. These solid fats separate out in the blood, like oil and vinegar in salad dressing. Insoluble, solid fats cannot circulate through the network of fine capillaries in the body; instead, they deposit along larger blood vessels walls, compromising circulation and promoting heart disease.
Olive oil is “mono-unsaturated” because it has only one double hitch on the carbon train. Olive oil is liquid at room temperature, but its single hitch ensures that the oil will solidify as it cools. The more double hitches on the train, the more fluid or “liquid” the train will be at room temperature and even cooler temperatures. “Polyunsaturated” oils have many hitches between the carbon boxcars and remain liquid even at low temperatures. Remember that multiple bonds also assure that the oil will associate with proteins and more easily dissolve in the blood.
Linoleic acid, one of the essential fatty acids, has two double bonds. Alpha-linolenic acid, the second essential fatty acid, has three double bonds. The first double bond on the linoleic molecule is at the sixth carbon (boxcar on the train), which is why linoleic acid is called an “omega-6” fatty acid. For alpha-linolenic acid, the first double bond is at the third carbon, which explains its designation as an “omega-3” fatty acid.
Most nutrition experts recommend that we maintain a ratio of three to four times more linoleic acid than alpha-linolenic acid (3:1 or 4:1 ratio). Eating the Standard American Diet (SAD), nutritionists estimate most Americans consume 20 times more linoleic than alpha-linolenic acid (20:1 ratio). That means most people eat five to seven times more linoleic acid than they need.
In normal, “physiological” amounts, linoleic essential fatty acid reduces inflammatory activity in the body. Too much of even “good” linoleic, however, can have the opposite effect by boosting inflammatory reactions. Re-establishing a normal ratio of essential fatty acids, i.e. reducing linoleic and increasing alpha-linolenic acid, can improve several conditions, including rheumatoid arthritis, atherosclerosis, high blood pressure, and possibly even cancer.
Fish oils are rich in the “good” omega-3 and omega-6 fatty acids. Studies demonstrate that supplementing fish oils can decrease blood pressure and lower cholesterol levels.2 Certain plant oils also contain high amounts of omega-3 and omega-6 fatty acids. Plant oils containing alpha-linolenic acid (listed below) may be healthier sources of omega-3 and omega-6 fatty acids than fish oils which tend to become rancid during the manufacturing process. Most fish oils also cost more than plant oils.
To establish a normal ratio of essential fatty acids, emphasize alpha-linolenic fatty acids in the diet. Remember that we need both essential fatty acids in the diet in small amounts.
Saturated fats (minimize or eliminate these):
- Animal fat, especially high in red meats
- Palm oil
Hydrogenated oils (eliminate these)
- Vegetable shortening
- Any packaged foods containing “hydrogenated vegetable oil”
Oils rich in linoleic essential fatty acid (small amounts of these):
- Evening primrose oil
- Black currant seed oil
- Borage oil
- DHA (fish oil)
Oils rich in alpha-linolenic essential fatty acid (emphasize these):
- EPA (fish oil)
- Flaxseed oil (the richest natural source of omega-3 fatty acids)
- Pumpkin seeds and oil
- Hemp seeds and oil
Quality is as important as quantity of fat
Choose oils and fats as close as possible to their natural state. Most margarines are made with altered fats called “trans fatty acids.” Remember chemistry class and those noxious fumes you generated under the laboratory hood? One of the few concepts from organic chemistry that still serves me is the understanding of cis and transmolecular formations, which describes the three-dimensional structure of the molecule.
Normally the hydrogen atoms attached to carbon in a fat molecule are in the same plane, on the same “side” of the molecule (cis formation). Think of the train with hydrogen atoms attached to the top of the boxcar. Heating fat molecules and adding hydrogen atoms changes the molecular structure. These altered trans fatty acids have hydrogen molecules attached to the top and bottom of the boxcar, across from (“trans”) each other (on opposite sides of the boxcar). Because of this extra hydrogen bumping along the “tracks” at the bottom of the molecule, these fats do not flow as easily in the body. They are more solid at room temperature outside the body and inside the body.
Over-heating “good” polyunsaturated oil breaks the “double hitches” between the carbon boxcar, and hydrogen atoms fill the missing gaps. Remember that the fewer the “hitches” or bonds, the more solid the oil is at room temperature. The added hydrogen atoms bond on the top and bottom of the boxcar, which further stabilizes the molecule. In essence, heating and hydrogenating vegetable oils changes them from “good” poly-unsaturated oil to “bad” saturated fat.
Think about the difference between a baked and a fried potato. The baked potato remains soft. The fried potato becomes “crispy,” or more solid. At high temperatures, the “good” vegetable oil used to fry the potato transforms into a trans-fatty acid, causing the crispier, more solid texture. The fried food may taste good, but we lose the beneficial features of the polyunsaturated vegetable oil and gain the health destroying effects of trans-fatty acids.
These trans-fatty acids became more widely available with the introduction of margarine to replace butter, a scarce commodity during the Great Depression of the1930s. After WWII, food manufacturers began to incorporate these altered oils in processed foods such as bakery products, peanut butter, and shortening. Today only the most vigilant can completely avoid trans-fatty acids.
Only now are we beginning to understand the long-term effects of consuming trans-fatty acids. A study published in Lancet, the premier British medical journal, demonstrated that women eating a diet high in trans-fatty acids (e.g. margarine, vegetable shortening, and fried foods) have much higher risk of developing coronary heart disease.3 In contrast, people eating a “Mediterranean” diet, high in fresh vegetables, fruits, fish, and olive oil, have significantly lower risk of heart disease.4
Remember that fatty acids compose the cell wall of every cell in our body. The increased incidence of many chronic diseases is in part a side effect of incorporating these altered fats, e.g. trans-fatty acids and hydrogenated oils, into our cell walls. Normally polyunsaturated oils create “smooth,” slippery cell walls. Trans-fatty acids, however, create a jumbled breach, like an unmatched wooden board, in the cell wall. Nutrients cannot move as easily in, nor wastes out through the cell wall. In short, all metabolic reactions in the cell would be disturbed.
How much fat do I need in my diet?
In a previous section we discussed the ideal ratio of essential fatty acids. Now let’s look at the recommended quantity of fat in the diet. Usually dietary recommendations suggest the ideal percentage of calories derived from fat rather than a specific amount. For people consuming a traditional Asian diet, about 10 percent of their calories come from fat. To achieve this truly low fat diet means cooking with little or no oil. The vast majority of fat on a 10 percent fat diet naturally occurs in the foods. Whole grains, for example, contain tiny amounts of oil, as do vegetables. Nuts and seeds contain higher amounts of naturally occurring oils. The low fat content of the Asian diet may account for lower breast and colon cancer rates as well as a host of other chronic disease. In contrast to the Asian diet, most North Americans derive a prodigious 40 to 50 percent of their calories from fat!
What kinds of oils should I choose?
Remember that the type of fat you eat may be as important as the quantity. Someone may report jubilantly that they have reduced their fat consumption to 20 percent of their daily calories, but if the majority of that fat is from hydrogenated margarine, they have little reason to celebrate.
Aim for a diet with 10 to 15 percent of your calories derived from fats. Ideally those fats would be naturally occurring oils in the food you eat, supplemented with olive oil for cooking and small amounts of flax or other cold-pressed oils for salad dressings.
Nuts and seeds are good sources of natural oils. You need only a small quantity – a handful, or a couple of tablespoons of a seed or nut, to fulfill your daily needs for oil. Make sure you are eating fresh nuts and seeds. All oils, even naturally occurring oils, may become oxidized, or “rancid.” Once fat or oil oxidizes, it does more harm than good in the body.
An “oxidized” food contains free oxygen, which acts as a “free radical” in the body. No, this is not a flashback from the Seventies – a “free radical” is a substance with oxygen attached. Obviously we need oxygen in the air we breathe to nourish every cell in the body. Too much oxygen, or oxygen in the wrong place, however, can damage the body. The body keeps very tight control over oxygen absorption and transport in the body. Carbon quickly combines with oxygen waste to form CO2, carbon dioxide. Other substances, known as “anti-oxidants,” also combine with and neutralize oxygen. If oxygen had free reign in the body with no regulation whatsoever, oxygen would “oxidize,” or damage, the cells in our body.
Eating rancid oils is an easy way to ingest a host of “free radicals.” The body then has to expend a lot of nutrients and energy to chase down and attach something to those free-ranging oxygen molecules. If our body has to allocate many of its resources to remedy the side effects of rancid food, we have less energy to take of other important business, like nourishing and repairing cells.
Oils may go rancid even before they have the characteristic stale, bitter smell. If a jar of nuts or seeds smells rancid, they have long since passed the healthful eating stage. Any food, for that matter, that smells rancid is a good candidate for the compost heap or the trash can. “Wasting” rancid food by tossing it in the garbage is a better choice than trashing the body with a host of free radicals.
The same wisdom holds true for oils. If oil smells stale, it has long since become rancid. Discard these oils immediately. You can increase the longevity of oils by keeping them in a cool, dark place, e.g. in the refrigerator. Even olive oil should be refrigerated. If refrigerated olive oil hardens, simply place the bottle in a bowl of warm water for a few minutes, and the oil will melt to liquid again. You also can store olive oil in a wide-mouth canning jar. Simply spoon out olive oil as you need it for cooking.
Most manufacturers extract oils from nuts or seeds with chemicals and heat. Remember that heat changes the “hitches on the boxcars,” the configuration of the oil molecule. Cold-pressed oils are a better choice than conventionally extracted oils. These cold-pressed oils may cost a bit more, but they are worth the savings in the free radical clean up the body has to do.
Exposing the “fake” fat
Olestra, Procter and Gamble’s new alternative to oil, cannot be absorbed in the digestive tract. “Eureka!” you may think. “All the wonderful taste of fat without the calories!” Unfortunately Olestra quickly exits the digestive tract along with other oil-soluble nutrients like vitamins A, E, and D. Lycopene is one the strongest anti-oxidants known. One serving of Olestra causes a 60 percent drop in lycopene absorption. Focus on naturally occurring oils, not high tech substitutes that strip the body of vital nutrients.
1 Budwig, Johanna. Flax Oil as a True Aid Against Arthritis, Heart Infarction, Cancer, and other Diseases. Vancouver, BC: Apple Publishing Company, Ltd, 1992 & 1994, 7.
2 Burr, M.L. et al. “Effects of changes in fat, fish, and fibre intakes on death and myocardial reinfarction: diet and reinfarction trial (DART),” Lancet ii (1989): 757-761.
3 Willet, W.C. et al. “Intake of trans fatty acids and risk of coronary heart disease among women,” Lancet 69 (1993):3-19.
4 De Lorgeril, M. et al. “Control of bias in dietary trial to prevent coronary recurrences: the Lyon diet heart study,” Eur J Clin Nutr 51 (1997): 116-122.